diff --git a/.github/workflows/export-dynamic.yaml b/.github/workflows/export-dynamic.yaml
index 25d7ebdb..a89058d8 100644
--- a/.github/workflows/export-dynamic.yaml
+++ b/.github/workflows/export-dynamic.yaml
@@ -128,6 +128,16 @@ on:
         description: Optional commit ID of the last successful publishing of plugin container images
         type: string
         required: false
+
+      prepare-downstream-sources:
+        description: >
+          When true, after a successful plugin export run the prepare-sources CLI
+          (prepare-rhdh-supported-sources) to transform the workspace into a
+          prepared downstream source tree. Default false leaves existing export
+          behavior unchanged.
+        type: boolean
+        default: false
+        required: false
             
     outputs:
       published-exports:
@@ -356,6 +366,52 @@ jobs:
           retention-days: ${{ inputs.artifact-retention-days }}
           overwrite: true
 
+      # RHIDP-15846: optional post-export prepare-sources pipeline.
+      # workspace-path uses plugins-root (. = flat repo; workspaces/<name> = non-flat).
+      # overlay-path is the checked-out overlay workspace directory (source.json).
+      # Until construct-artifact (RHIDP-15845) lands, upload the prepared tree as a
+      # workflow artifact instead of pushing an OCI image.
+      - name: Resolve prepared sources paths
+        if: ${{ inputs.prepare-downstream-sources && success() && steps.export-dynamic.outputs.failed-exports == '' && steps.export-dynamic.outputs.workspace-skipped-unchanged-since == 'false' }}
+        id: prepare-paths
+        env:
+          PLUGINS_ROOT: ${{ inputs.plugins-root }}
+          OVERLAY_ROOT: ${{ inputs.overlay-root }}
+        run: |
+          # Flat repos use plugins-root "."; upload-artifact rejects paths ending in "/."
+          if [[ "${PLUGINS_ROOT}" == "." || -z "${PLUGINS_ROOT}" ]]; then
+            echo "workspace_path=${GITHUB_WORKSPACE}/source-repo" >> "$GITHUB_OUTPUT"
+          else
+            echo "workspace_path=${GITHUB_WORKSPACE}/source-repo/${PLUGINS_ROOT}" >> "$GITHUB_OUTPUT"
+          fi
+          echo "overlay_path=${GITHUB_WORKSPACE}/overlay-repo/${OVERLAY_ROOT}" >> "$GITHUB_OUTPUT"
+
+      # $/ = self repository reference: resolves to this workflow file's repository
+      # at the running commit, even when called from the overlays repo. No checkout
+      # step needed, and the reference is commit-locked by definition.
+      - name: Prepare downstream sources
+        if: ${{ inputs.prepare-downstream-sources && success() && steps.export-dynamic.outputs.failed-exports == '' && steps.export-dynamic.outputs.workspace-skipped-unchanged-since == 'false' }}
+        id: prepare-downstream-sources
+        uses: $/prepare-sources
+        with:
+          workspace-path: ${{ steps.prepare-paths.outputs.workspace_path }}
+          overlay-path: ${{ steps.prepare-paths.outputs.overlay_path }}
+
+      - name: Upload prepared downstream sources
+        uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
+        if: ${{ inputs.prepare-downstream-sources && success() && steps.prepare-downstream-sources.outcome == 'success' }}
+        with:
+          name: prepared downstream sources${{ steps.set-artifacts-name-suffix.outputs.ARTIFACTS_NAME_SUFFIX }}
+          path: |
+            ${{ steps.prepare-paths.outputs.workspace_path }}
+            !**/node_modules
+            !**/.yarn/cache
+            !**/.git
+          if-no-files-found: warn
+          retention-days: ${{ inputs.artifact-retention-days }}
+          overwrite: true
+          include-hidden-files: true
+
       - name: Upload the project to workflow artifacts on failure
         uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
         if: ${{ inputs.upload-project-on-error && (failure() || steps.export-dynamic.outputs.failed-exports) }}
diff --git a/.github/workflows/export-workspaces-as-dynamic.yaml b/.github/workflows/export-workspaces-as-dynamic.yaml
index 5aa1dc99..0b0548ea 100644
--- a/.github/workflows/export-workspaces-as-dynamic.yaml
+++ b/.github/workflows/export-workspaces-as-dynamic.yaml
@@ -74,6 +74,15 @@ on:
         type: string
         required: false
 
+      prepare-downstream-sources:
+        description: >
+          When true, after a successful plugin export run the prepare-sources CLI
+          to transform each workspace into a prepared downstream source tree.
+          Default false leaves existing export behavior unchanged.
+        type: boolean
+        default: false
+        required: false
+
     outputs:
       published-exports:
         value: '${{ jobs.export.outputs.published-exports }}'
@@ -264,7 +273,12 @@ jobs:
   export:
     name: Export ${{ matrix.workspace.overlay-root }}
     needs: prepare
-    uses: redhat-developer/rhdh-plugin-export-utils/.github/workflows/export-dynamic.yaml@main
+    # Same-repo, same-commit as this workflow. Prefer "$/" over "./" — when overlays
+    # call this reusable workflow, nested "./" can resolve against the top-level
+    # caller (overlays) instead of utils. "$/" keeps export-dynamic in lockstep so
+    # new inputs (prepare-downstream-sources) are not dropped by pinning @main.
+    # https://docs.github.com/en/actions/how-tos/reuse-automations/reuse-workflows
+    uses: $/.github/workflows/export-dynamic.yaml
     strategy:
       fail-fast: false
       matrix:
@@ -289,6 +303,7 @@ jobs:
       target-backstage-version: ${{ needs.prepare.outputs.backstage-version }}
       last-publish-commit: ${{ inputs.last-publish-commit }}
       image-registry-user: ${{ inputs.image-registry-user }}
+      prepare-downstream-sources: ${{ inputs.prepare-downstream-sources }}
 
     secrets:
       image-registry-password: ${{ secrets.image-registry-password }}
diff --git a/.github/workflows/test-prepare-downstream-sources.yaml b/.github/workflows/test-prepare-downstream-sources.yaml
new file mode 100644
index 00000000..0d8fc94a
--- /dev/null
+++ b/.github/workflows/test-prepare-downstream-sources.yaml
@@ -0,0 +1,35 @@
+# Temporary RHIDP-15846 test harness — remove after AC sign-off.
+# Calls the same-repo reusable export workflow (fork→fork reusable calls startup-fail).
+name: Test Prepare Downstream Sources Export
+on:
+  workflow_dispatch:
+    inputs:
+      workspace-path:
+        description: Overlay workspace path (e.g. workspaces/topology or workspaces/backstage)
+        type: string
+        required: true
+        default: workspaces/topology
+      prepare-downstream-sources:
+        description: Exercise prepare-sources post-export steps
+        type: boolean
+        required: false
+        default: true
+
+jobs:
+  export:
+    uses: ./.github/workflows/export-workspaces-as-dynamic.yaml
+    with:
+      workspace-path: ${{ inputs.workspace-path }}
+      overlay-repo: redhat-developer/rhdh-plugin-export-overlays
+      overlay-branch: main
+      publish-container: false
+      upload-project-on-error: true
+      prepare-downstream-sources: ${{ inputs.prepare-downstream-sources }}
+      image-registry-user: ${{ github.actor }}
+    secrets:
+      image-registry-password: ${{ secrets.GITHUB_TOKEN }}
+    permissions:
+      contents: write
+      packages: write
+      attestations: write
+      id-token: write
diff --git a/prepare-sources/action.yaml b/prepare-sources/action.yaml
index 0f3a3200..83d0d9a2 100644
--- a/prepare-sources/action.yaml
+++ b/prepare-sources/action.yaml
@@ -17,7 +17,9 @@ runs:
       uses: voidzero-dev/setup-vp@3754dd7dbdb32bd8f6d28b6043de13ad3a75f21f # v1.21.1
       with:
         working-directory: ${{ github.action_path }}
-        cache: true
+        cache: false
+        # cache:true fails hashing package-lock.json when this action is fetched
+        # under _actions/ (composite reuse from export-dynamic). Install still runs.
         run-install: |
           args: ['--prod']